Electric motor-driven pumps



March 2, 1965 P. PENSABENE ELECTRIC MOTOR-DRIVEN PUMPS Filed March 25, 1963 'III/IIIIII NVE N T019.

,w u, m PEA/56 BtI/VE' United States Patent "cc 3,171,356 ELECTRKC MOTOR=DRIVEN PUMPS Philip Pensabene, Bristol Road, Bridgewater, England Filed Mar. 25, 1963, Ser. No. 267,435

4 Claims. (Cl. 103--87) This invention relates to electric motor-driven pumps, and more particularly to a small electric motor pump unit designed primarily for circulating water in central heating systems of domestic or other dwellings or premises. The electric motor employed with such pumps is of the disc type having co-axial stator and rotor armature discs with an axial magnetic operating gap separating the rotor poles from the stator teeth. Circulating pump units for such purposes are required to be very quiet in operation, but at the same time suificient torque must be available to enable the motor to start against adverse conditions, such as may be produced by lime or rust deposits lodging in the rotating parts of the pump. These two requirements are inimical due to the fact that a large electrical gap is necessary in the motor for silent running so as to minimize high frequency hum which is normally produced by the variation in flux density across the surface of the stator. On the other hand, to provide maximum torque for any given rotor or stator windings, it is necessary that the electrical gap shall be as small as mechanically possible.

The object of the invention is to bring compatibility between the aforesaid requirements.

According to the invention there is provided an electric motor-driven pump unit having means operable by the switching on of the motor, first to close the electrical gap of the motor to a high starting torque condition, and subsequently, when the motor is running at its on-load speed, said means is further operated by a difference in hydraulic pressure in the pump to open said gap to a quiet running condition.

In the usual unit designed for small bore circulating heating systems of the domestic dwelling type, there is employed a disc type motor, and the motor rotor and pump impeller form a single assembly, and the invention provides that the said assembly is mounted for axial displacement between stops which define minimum gap/ high starting torque, and maximum gap/quiet running positions respectively, said assembly being of a magnetic material or having a magnetic material element located adjacent to the face of the motor stator so as to be magnetically attracted by and effect displacement of the assembly into the minimum gap/high torque position for starting the motor when the stator is energized, and the pump is provided with hydraulic discharge and suction chambers which are so arranged that as the pump gathers speed a hydraulic thrust arising from a pressure ditference between said chambers is applied to the said assembly in opposite direction to the magnetic pull so as to cause the assembly to be in the other of said positions when the motor is running at its on-load speed.

The rotor assembly is preferably mounted to rotate and be axially adjustable upon a stationary shaft at opposite ends of which are carried said position-defining stops, as will hereafter be understood by reference to the accompanying drawings which illustrate a convenient embodiment of the invention, and in which:

FIGURE 1 shows a sectional elevation of the unit in the minimum gap high torque position of the rotor assembly, and

FIGURE 2 is a similar view with the rotor assembly in the other position of maximum gap/quiet running.

The unit comprises a casing divided by a Waterproof diaphragm 3 into a motor stator compartment 1 and a pump compartment 2. The diaphragm separates the 3,171,356 Patented Mar. 2, 1965 stator 4 of the motor from the rotor assembly which runs in the hydraulic circuit including a suction chamber 5 and a discharge chamber 6 formed in the pump compartment 2 by a dividing wall 2a with a fluid flow channel 2b at the centre. The diaphragm 3 lies against the stator teeth and defines one side of the magnetic gap 7, the other side of which is constituted by the poles 8 of the disc rotor armature 9 having on the pump side, pump impeller blades 10, and being mounted (for example integral as shown) on a hub 10a with a metal bearing bush 11 to constitute the aforesaid rotor assembly. The rotor 9 in this instance is made of iron or embodies magnetic material adjacent to the face of the stator defined by the diaphragm 3.

The said rotor assembly is rotatably supported and has a predetermined axial displacement upon a stationary shaft 12 which is fixed to the pump casing 2 by a single screw 13 which also locks in position against the end of the shaft a thrust Washer 14 which is made of a nonmagnetic or any convenient material. This thrust Washer 14 forms part of a stop which defines the minimum gap/high torque position of the assembly, and co-operates with a thrust face 15 at the end of the bush 11 of the assembly.

At the opposite fixed end of the shaft, another pair of thrust elements are provided to provide the stop for defining the maximum gap/quiet running position of the assembly. Thus, fixed to the hub of the assembly is a thrust washer 16 which co-operates with a thrust flange 17 on the stationary shaft 12.

FIGURE 1 shows the position of the parts of the pump motor unit when the electric motor has been switched on to energise the stator 4. The resulting magnetic pull produce delectrically by the stator windings applies a traction pull to the rotor assembly. In consequence, the rotor assembly is drawn axially towards the stator until the stop elements 14, 15 come into engagement. Such axial dis placement reduces the electrical gap 7 between the rotor 8 and the stator 4 to the smallest mechanical dimension, thus giving a very high starting torque.

As the rotor assembly gathers speed, the hydraulic thrust which is produced by the impeller 10 due to the difference between the pressures in the two chambers 5 and 6, overcomes the magnetic pull of the stator so as to cause the rotor assembly to slide along the stationary shaft 12 away from the stator until the thrust elements 16 and 17 engage, as shown in FIGURE 2, thus increasing the electrical gap to the maximum 7' so as to provide, at the full speed on load condition of the motor, for quiet running.

The construction shown by employing the disc type electric motor ensures a compact unit which can be made to a convenient size suitable for small bore heating installations while giving the desired compatibility of requirements, as stated.

I claim:

1. A hydraulic pump unit comprising a casing divided by a diaphragm into a motor stator compartment and a pump compartment, a disc type electric motor having a stator mounted in the stator compartment and a disc rotor armature mounted in the pump department coaxial with the stator and having poles at the periphery separated from the stator by a magnetic air gap including the diaphragm, said pump compartment having a suction chamber and a discharge chamber next to the diaphragm, a hydraulic pump impeller mounted in said discharge chamber to rotate with the rotor armature as an assembly to provide differential hydraulic pressure between said chambers resulting in axial thrust on the impeller in a direction away from the diaphragm, and mounting meansfor the assembly providing limited axial displacement of the assembly in one direction by said thrust to an open gap 3 running position and in the opposite direction to a closed gap high starting torque position of the armature.

2. A hydraulic pump unit comprising an axial gap disc type electric motor having a rotor armature which is axially displaceable to vary said gap, a hydraulic circuit including a pump impeller driven by said rotor means whereby in the stationary position of the rotor a magnetic pull across the gap displaces the rotor axially in one direction into a closed gap high torque starting position, and means whereby differential hydraulic pressure is created in said circuit by the impeller gathering speed and displaces the rotor in the opposite direction to an open gap on load minimum torque running position.

3. A hydraulic pump unit according to claim 1 where in the said mounting means comprise a fixed shaft in the casing projecting inwardly towards the diaphragm, a hub to said assembly rotatably slidable on said shaft, and complementary thrust faces on shaft and hub respectively at each end of the shaft to constitute stop's limiting the axial displacement of said assembly in each of said directions.

4. A hydraulic pump unit, comprising an axial gap disc type electric motor having a rotor armature which is axially displaceable to vary said gap between closed and open positions, signifying high torque starting and minimum torque running conditions respectively, a hydraulic circuit including a pump impeller constructed as an assembly to be driven by said motor, and means for creating differential hydraulic pressure in said circuit including a high pressure surface on one side of the assembly for displacing the assembly to the open gap portion of said rotor armature.

References Cited by the Examiner UNITED STATES PATENTS 2,727,163 12/55 Meyer 103-87 2,824,520 2/58 Bartels 103-97 2O LAURENCE V. EFNER, Examiner. 

1. A HYDRAULIC PUMP UNIT COMPRISING A CASING DIVIDED BY A DIAPHRAGM INTO A MOTOR STATOR COMPARTMENT AND A PUMP COMPARTMENT, A DISC TYPE ELECTRIC MOTOR HAVING A STATOR MOUNTED IN THE STATOR COMPARTMENT AND A DISC ROTOR ARMATURE MOUNTED IN THE PUMP DEPARTMENT COAXIAL WITH THE STATOR AND HAVING POLES AT THE PERIPHERY SEPARATED FROM THE STATOR BY A MAGNETIC AIR GAP INCLUDING THE DIAPHRAGM, SAID PUMP COMPARTMENT HAVING A SUCTION CHAMBER AND A DISCHARGE CHAMBER NEXT TO THE DIAPHRAGM, A HYDRAULIC PUMP IMPELLER MOUNTED IN SAID DISCHARGE CHAMBER TO ROTATE WITH THE ROTOR ARMATURE AS AN ASSEMBLY TO PROVIDE DIFFERENTIAL HYDRAULIC PRESSURE BETWEEN SAID CHAMBERS RESULTING IN AXIAL THRUST ON THE IMPELLER IN A DIRECTION AWAY FROM THE DIAPHRAGM, AND MOUNTING MEANS FOR THE ASSEMBLY PROVIDING LIMITED AXIAL DISPLACEMENT OF THE ASSEMBLY IN ONE DIRECTION BY SAID THRUST TO AN OPEN GAP RUNNING POSITION AND IN THE OPPOSITE DIRECTION TO A CLOSED GAP HIGH STARTING TORQUE POSITION OF THE ARMATURE. 